Producing calcium nitrate from dolomite while simultaneously obtaining magnesia



Patented Apr. 18, 1933 A..-G., OF CASTROP-RAUXEL, GERMANY, A CORPORATION OF G ERMANY I i k um E s lms A EN orncs;;;; j

meNEsIA No Drawing. Application filed March-29, 1932, Np, ti-301,878, and in Germany March 3,1331. 1

This invention relates to a method ofproducing calcium nitrate from dolomlte whlle simultaneously obtainingmagnesia.

, I It has been proposed already, to produce calcium nitrate from dolomite and .to obtain also magnesia therefrom by V dissolving dolomite in nitric acid, precipitating magnesia from the solution by means of lime, especially-in the form of burnt dolomite, filtering it ofi, subjecting it to further treatment, and exposingthe filtrate to evaporation to produce solid calcium nitrate. It has further been proposed to produce calcium nitrate and to obtain, atthe same time, magnesia by treating burntudolomite withnitric acidf corresponding in quantity to that of the lime present, and then to separate the lime from the magnesia by dissolving it out.

The known methods, however, have not attained practical importance, for experiments have shown that it is not possible to keep the magnesia free from lime to a suflicient degree and to obtain a really useful grade of calcium nitrate. For industrial use, the lime contents of magnesia must not exceed 4%, while calcium nitrate containing magnesium nitrate is rendered still more hygroscopic and becomes unfit for fertilizing purposes.

The invention eliminates these drawbacks in a simple and economical way by employing for precipitating the magnesia from the dolomite dissolved in nitric acid, or for dissolving the lime out of the burnt and slaked dolomite, milk of lime or milk of dolomite that has previously been filtered through fine sieves or from which all particles except the very fine ones have been removed by suit able centrifugal devices. Ordinary milk of lime or dolomite obtained by slaking quicklime or burnt dolomite leaves, for example, a residue of 10% and more on a sieve having 4900 meshes, and it has been found that this is the reason why magnesia during the prenitrate.

solution,

o'r'ro KIBPE, or osivnaucx, A'ssIeNon or ONE-HALF TO no'oxnnn-wnnx'n PRODUCING oncmm lvlrnamnrnom'nonommn WHILE smemmaousw OBTAINING 'cipitating or dissolving step cannot be kept deficient in lime, as the coarser particles, re-

act only .on .the surface. Furthermore, the

calcium nitrate already formed. will have a gel-forming effect upon themagnesium hy- I p Emamplc 1 I '100kilos of raw dolomite of-3 1% CaO and 20% MgO contents are dissolved in 300 liters nitric acid having a specific gravity of..1.2. To this solution 19.0 liters milk. of lime are added while .stirring,. which contains 140 been filtered.

grams 'CaO' per liter and I has through a -sieve of 4900 meshes? :Gon'version takes place-quickly and perfectly. 1' The precipitated magnesium hydroxide is separated from the calcium nitratelyeby means of a filter press or suction filter and washed out with water to which nitrate solution or unwed-nitric acid has been added if necessary until the washing Water shows a specific gravity of 1.01'. The-magnesium hydroxide .is'dr'ied, calcined orsinter'ed asrequired,

The yield amounts to abo'ut 20 kilos"mag- *nesia which, according to its composition or the addition of ferrous salts to the dolomite contains the requisite amounts F6203 or other sinter substances. :Itis easy toj-keep the lime content below 3% andeven below 1%.- The filtrate is then subjected .in

i Precipitation is carried out preferably so as to keep the temperaturebelow f,"t'he dolomite solution and-the milk of lime or magnesia deficient in'lime' and. purecalcium theknown way'to evaporation to obtain solid calcium nitrate, 164 kilos ofwhich possessing a-high degree of purity being thusobtained from 100 kilos dolomite.

' to 167 kilos; 1 p, r Duringthe production of milk of dolomite a. considerable residue is" left after the fine conversion heat is developed which, at higher temperatures, will have an unfavorable effect vupon the magnesium hydroxide by rendering 100 kilos of raw dolomite of 34% Ca(), and 18% MgO Contents are dissolved in 300 liters I nitric acid.- In the meantime, 40 kilos burnt dolomite areslaked in about 17 5 liters'pf water and passedth'rough a 4900 mesh sieve.

This milk is then added While stirring'to' they -.'dolomite solution mentioned above, wheres,

cium nitrate lye byv means of a filter press,

'sution filter orthelike." Theyield amountsr V vto 31 kilos magnesia, since the magnesia lithe mflk havmg Prevlously e filtered the dolomite milk must be counted also. This magnesia, too," is deficient in lime and con-1' tainstonlyj 9.813% thereof, sothat itis very "useful, The yield of calcium nit-rateamounts sieving step, which 'is preferably dissolved in nitric acid and used as nitrate solution! T On. the other :hand, if, .for special reasons,

"such asto save freight, burnt dolomite exclusively bothffor dissolution in nitricacid erably carried on so that the burnt dolomite.

is slaked in Water and,after settling, the milk of'dolomite passedthroughthe sieve in 'quantities corresponding approximatelyt to onei'gethe'rwith the residue, and to this solution or, by means oi alkali sulfates or alkali chlo-r rides, converted into alkali saltpeter for which this calcium nitrate is particularly suited on account of its high degree of purity.

The yield of magnesia and calcium nitrate are almost quantitative,the magnesia having only 1.01% CaO contents.

The sifting residue is utilized by preferably dissolving it in the nitric acid.

1; A-rmaethod oi producing calciumnitrate, and simultaneously obtaining magnesia, from i e ei elsee e in eissues th d 15 upon gn ia separated-10m thecale. mltqlnllltrlc 1 Z L-P eclpltatms through fine sieves;

42, A, method f producing calcium nitrate,

and simultaneously obtaining magnesia, from 'dolomite,.consisting in dissolving 'the=dolomite in nitric acid! and 'preci-pitating magnesia by means off a ma-te'rial in the group consisting ofn'ilk or lime and of dolomite, the milk jhaving-previously been freed from .all exceptflthe finest 5 partioles -by suitable devices? I methodas claimed claim 1', accordbig towhichv 'the dolomite is first burnt, r and for prcipitation, the Operation r sla ked and then treatedzwith, nitr c ac d,

4:. 'A method'as claimed in claim 2, according to which the dolomitedsfirst burnt, slaked andthen treated with nitricacid'. H I

In testimony whereof I have afiixed *m'y half: of the amount of dolomite used: The fi v v i i i rest,'which contains burnt, overburnt and uni burntuparts, is: dissolved in'nitriciacid toiszthen-addedthe strained milk-0f dolomite, v

after cooling if necessary, or the nitric acid Ewample3 solution of dolomite may be addedito the V strained milk of limeor'dolomite-m; I

Of-ea at;

H liters of waterto'form milk ofdolomitewhich 1 r is then passed-through a 4900-mesh sieve.

Tothis milk, whichpreferably is cooled down calcium nitrate-while the' magnesia' remains to 20centigrade orless,7 liters ofnitric'acidi having a specific gravity of-1.32 are'gradually l v added under constant stirring'and good 0001- undissolved incoagulated conditionmrhe magnesia -or:magnesium hydroxide is sepafurther. treatment as required. ''The filtrate turned into calciumnitrate by evaporation rated from the calcium nitrate lye-by-means I of a filtering cloth, suction 'filter or filter press v li id hasa specific gravity of 1.01, which .is dried, calcined, 'sintered, and subjected to 

